1. Field of the Invention
The present invention relates to an image pickup device having an image input optical system for forming an image on light receiving portions of an image sensor such as a CCD sensor or a CMOS sensor.
2. Description of the Prior Art
An image sensor has light receiving portions arranged in a matrix, and vertically transferring portions for transferring charges generated by the light receiving portions in a vertical direction. FIG. 11 is a cross-sectional view showing one pixel of the image sensor. A photodiode (light receiving) portion 5′ constituting the light receiving portion and a vertical register portion 6′ constituting the vertically transferring portion are disposed on a silicon layer 10 serving as a substrate. An insulative film 11 such as SiO2 is formed on the silicon layer 10. An electrode 8 for charge transfer is disposed on the register portion 6′. An aluminum light intercepting film 7 is disposed over the register portion 6′ and over a part of the photodiode portion 5′. Because of the presence of the light intercepting film 7, no light is directly incident on the top of the register portion 6′. In order that no light is incident on the register portion 6′ from a slanting direction, a predetermined distance d is set between the register portion 6′ and the light receivable part of the photodiode portion 5′.
However, the light receiving portions of the image sensor are longitudinally elongated in one column, whereas the luminous flux from an image input optical system for inputting light to the image sensor is circular in cross section. For this reason, part of the input luminous flux is incident on areas outside the light receiving portions, and further, in the part of the luminous flux that is obliquely incident on the light receiving portions, the part incident on areas outside the light receiving portions corresponds to the light A in FIG. 11 being obliquely incident to reach the adjacent register portion 6′, so that smears are generated. As a result, an output of high image quality cannot be obtained. Some of the luminous flux turns to reach the side of the register portion 6′ to affect the register portion 6′ after reflected at the light intercepting film like the light B.